1) Field of the Invention
The present invention relates to a shield for space optics and, more particularly, to a shield for protecting space optics from heat and contamination.
2) Description of Related Art
Interceptors, such as missiles or rockets for air defense, use various techniques for in-flight guidance in order to identify and/or engage airborne objects. If the interceptor is searching for a ballistic missile, the interceptor must not only be capable of tracking the missile but also distinguishing between the missile and any decoys. Examples of in-flight guidance techniques include devices, technologies, and media using infrared or visible cameras or detectors, LADAR, transducers, or other sensors, including sensitive components such as lenses, mirrors, lasers, or fiber optics, to transmit or detect light, other electromagnetic energy such as millimeter waves, or other forms of energy, such as sound waves.
Interceptors that employ optical systems for targeting include optics and electronics that are susceptible to overheating and contamination. In particular, during launch and at high speeds, the interceptor is subjected to frictional heating from air passing at high speeds over the interceptor causing increased temperatures that re-radiate to the optical surfaces and electronic assemblies. In addition, vibration caused during launch and flight frees particulate contamination from the interior of the interceptor that may re-deposit on the optical surfaces. As a result of the heat and contamination, the optical system will provide a lower signal-to-noise ratio due to obscuration from contaminants, increased infrared background from contamination and heating, and blurring due to warping of the optics from heating.
Different techniques have been developed to protect the optical system while airborne. One technique is to use a cover or group of covers that are positioned proximate to the nose of the interceptor and over the optical system while the interceptor is airborne. The cover(s) are later pivoted, ejected, or otherwise moved with mechanical devices to allow the optical system to operate. However, this system cannot provide protection from heat and contamination proximate to the cover itself and its deployment.
Another technique for protecting the optical system is a shroud that is disclosed in conjunction with an aircraft, where the shroud typically conforms to the nose of the aircraft and may later be deployed and, therefore, removed once the aircraft reaches a designated speed. U.S. Pat. No. 4,850,275 to Utreja et al. discloses a shroud positioned fore of a hollow nose portion that may be removed once the aircraft reaches a designated speed. The nose portion includes an optical window positioned aft of the shroud such that when the shroud is removed, the optical window is revealed. The shroud is designed to be detached automatically from the nose portion once the airplane obtains a desired altitude and/or speed. Within the nose portion, a nose cavity includes a base annularly surrounded by a rim. The optical window is integral to the base of the nose cavity, where the base is formed deep within the cavity to minimize convective heat flow along the base portion and conductive heat flow along the rim and cavity walls. The cavity of the nose portion is configured to lower the heat transfer coefficient and the unsteady density fluctuations about the optical window. However, there is no protective shield between the shroud and the optical window such that the optical window is still susceptible to heat radiation and contamination traveling from the interior of the shroud and through the nose cavity, which increases the probability for blurring of the optical system. In other words, while the shroud protects the optical window and the optical system that communicates through the optical window from external communication, the optical window is not protected from contamination originating from the shroud itself.
It would therefore be advantageous to provide a protective shield that is capable of protecting systems disposed within a launch vehicle, such as from heat and contaminants. It would also be advantageous to provide a protective shield that is capable of being deployed from the launch vehicle with a shroud. It would further be advantageous to provide a protective shield that is inexpensive and easily removed when deployed.